1. Field of the Invention
The present invention relates generally to a method and apparatus for managing forward control channels in a mobile communication system, and more particularly, to a method and apparatus for transmitting/receiving data over a Forward Shared Control Channel (F-SCCH), adapted to support various antenna technologies for data transmission in a forward link of a mobile communication system using multiple transmit/receive antennas.
2. Description of the Related Art
The mobile communication system has evolved into a high-speed, high-quality wireless packet data communication system that provides data services and multimedia services in addition to the early voice-oriented services. Recently, various mobile communication standards, such as High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), both defined in 3rd Generation Partnership Project (3GPP), High Rate Packet Data (HRPD) defined in 3rd Generation Partnership Project-2 (3GPP2), and IEEE 802.16, have been developed to support the high-speed, high-quality wireless packet data communication services.
The existing 3rd Generation wireless packet data communication systems, such as HSDPA, HSUPA and HRPD, use technologies of an Adaptive Modulation and Coding (AMC) method and a channel-sensitive scheduling method to improve the transmission efficiency.
With the use of the AMC method, a transmitter can adjust the amount of transmission data according to the channel state. That is, when the channel state is not ‘Good’, the transmitter reduces the amount of transmission data to adjust the reception error rate to a desired level, and when the channel state is ‘Good’, the transmitter increases the amount of transmission data to adjust the reception error rate to the desired level and to efficiently transmit a large volume of information.
With the use of the channel-sensitive scheduling-based resource management method, the transmitter selectively services the user having a good channel state among several users, thus increasing the system capacity compared to the method of assigning a channel to one user and servicing the user with the assigned channel.
The capacity increase is referred to as ‘multi-user diversity gain’. In sum, the AMC method and the channel-sensitive scheduling method are methods of applying the appropriate modulation and coding techniques at the most-efficient time determined depending on the partial channel state information fed back from a receiver.
To realize the AMC method and the channel-sensitive scheduling method, the receiver should feed back the channel state information to the transmitter. The channel state information that the receiver feeds back in this way is referred to herein as a ‘Channel Quality Indicator (CQI)’.
Recently, intensive research has been conducted to replace Code Division Multiple Access (CDMA), the multiple access scheme used in the 2nd and 3rd generation mobile communication systems, with Orthogonal Frequency Division Multiple Access (OFDMA) in the next generation system. 3GPP and 3GPP2 have started their standardizations on the evolved systems employing OFDMA. It is generally known that the OFDMA scheme, compared to the CDMA scheme, can expect the capacity increase. One of the several causes bringing about the capacity increase in the OFDMA scheme is that the OFDMA scheme can perform scheduling in the frequency domain (Frequency Domain Scheduling). As though the transceiver acquires capacity gain according to the time-varying channel characteristic using the channel-sensitive scheduling method, the transceiver can obtain the higher capacity gain with use of the frequency-varying channel characteristic. However, to support the frequency domain scheduling, the transmitter should previously acquire channel state information separately for each frequency. That is, the transmitter needs CQI feedback information for each frequency, causing an increase in the load due to the CQI feedback transmission.
In the next generation system, intensive research is being conducted on the introduction of Multiple Input Multiple Output (MIMO) technology employing multiple transmit/receive antennas. The term ‘MIMO’ as used herein refers to a technology that simultaneously transmits multiple data streams over the same resources using multiple transmit/receive antennas. It is well known that when the channel state is ‘Good,’ it is possible to increase the throughput at the same error rate by transmitting multiple low-modulation order data streams rather than increasing the modulation order. In the MIMO technique, the dimension over which an individual data stream is transmitted is referred to as a ‘layer’, and the method that applies AMC separately according to the channel state of the layer is efficient in increasing the capacity. For example, Per Antenna Rate Control (PARC) is a technology in which every transmit antenna transmits a different data stream, and in this technology, the layer is a transmit antenna. The multiple transmit antennas experience different channels, and the PARC technique applies AMC such that a larger amount of data can be transmitted via the transmit antenna having a good channel state and a less amount of data can be transmitted via the transmit antenna having a poor channel state. As another example, in Per Common Basis Rate Control (PCBRC) the layer is a fixed transmission beam. Therefore, the PCBRC technique transmits a greater amount of data over the transmission beam with a good channel state, and transmits a less amount of data over the transmission beam with a poor channel state.
Commonly, the packet mobile communication system using multiple antennas transmits/receives control information using a Forward Shared Control Channel (F-SCCH). The F-SCCH is a channel transmitted along with the transmission data when data is transmitted to an arbitrary terminal at an arbitrary time, and this channel is characterized by including the control information necessary for demodulation of the transmission data. Using Table 1 below, the constituent fields of F-SCCH will be considered. Table 1 shows a message format of the shared control channel, and the message is transmitted over the shared control channel. Besides the fields defined in Table 1, other fields used for performing other functions can be added to the shared control channel, and/or the number of bits used for expressing each of the fields is subject to change.
TABLE 1Block Persis-Ext. FieldtypeMACIDtentChanIDPFTXRank# bits29-1116-84-612FLAM00111110MCW01111110FLAM1MCW10100310FLAM2SCW 11111111FLAM
Referring to Table 1, ‘Block type’ is a field indicating a type of the message. ‘MAC ID’ is a field indicating an identifier (ID) of a terminal. That is, after receiving a shared control channel, the terminal checks MAC ID included in the received shared control channel to determine whether the received MAC ID is equal to a MAC ID previously agreed upon between the terminal and a base station, and thus determines whether there is any data being transmitted to the terminal itself. Although the MAC ID is included in the message of the shared control channel in Table 1, by way of example, the MAC ID can also be transmitted by scrambling the message of the shared control channel using a MAC ID-specific scrambling sequence of the target user. A ‘Persistent’ field is a field indicating whether the resource assigned to the terminal itself is persistent resource or non-persistent resource.
‘Channel Identifier (ChanID)’ is a field indicating an identifier for the assigned resource. ‘Packet Format (PF)’ is a field for notifying a modulation order, such as QPSK, 8PSK and 16QAM, used for data transmission, and a code rate. ‘Extended Transmission (Ext. Tx)’ is information indicating a time length of transmission data. ‘Rank’ indicates the number of data streams transmitted via multiple antennas. ‘Forward Link Assignment Message (FLAM)’ indicates that the message is a message for resource assignment for the forward link.
‘Multi CodeWord (MCW)’ indicates that when multiple data streams are transmitted via multiple antennas, the multiple data streams are streams that have undergone channel coding (for example, turbo coding) independently of each other. ‘Single CodeWord (SCW)’ indicates that when multiple data streams are transmitted via multiple antennas, the multiple data streams are parts of one codeword that has undergone channel coding.
In Table 1, numerals shown in the shaded blocks indicate whether each of the message types include a particular field. For example, FLAM has a Rank field=0, but SCW FLAM includes the Rank field. This means that the FLAM, as it is a message type used for Single Input Multiple Output (SIMO) transmission, does not need the Rank field used for transmission of multiple data streams, whereas the SCW FLAM needs the Rank information as multiple data streams can be transmitted.
However, the message format of the foregoing conventional shared control channel does not support precoding and/or various types of pilot patterns. When a common pilot is used, it is necessary to separately notify which precoding is applied thereto, because the pilot has not undergone precoding. However, when a dedicated pilot is used, it is necessary to separately notify which pilot pattern is used therefor. The conventional technology, however, gives no definition of the field for notifying such information.